Kinetics of rectus femoris stiffness, architecture, and muscle damage biomarkers in response to deceleration intensity during repeated sprints
摘要
Horizontal deceleration (DEC) underpins sudden velocity changes in intermittent sports, but the DEC intensity-induced effect during repeated-sprint ability (RSA) on muscle and recovery kinetics are underexplored. Twelve participants randomly performed an RSA protocol [3 sets of 8 × 20 m; 20-s passive recovery, 5-min rest] i) without DEC constraint post-sprint (DECfree), ii) with moderate enforced DEC (DEC10; 10-m braking distance post-sprint), and iii) with intense enforced DEC (DEC5; 5-m braking distance). DEC performances, rectus femoris stiffness and architecture and creatine kinase concentrations ([CK]) were assessed at Baseline, immediately after each set, and Post-24 h, -48 h and -72 h. Mean DEC was larger in DEC5 than in DEC10 and DECfree (both p < 0.001), and larger in DEC10 than in DECfree (p < 0.001). Relative shear modulus peaked at Set 3 (p = 0.021) irrespective of condition, but was higher in DEC5 than DECfree at Set 2, Set 3, Post-24 h and -48 h (all p ≤ 0.018), and higher than DEC10 at Set 3 and Post-24 h (both p ≤ 0.039). Muscle thickness was higher in DEC5 and DEC10 compared to DECfree (both p ≤ 0.004), whereas pennation angle and fascicle length showed no effects (all p ≥ 0.293). Relative [CK] exceeded Baseline at all time points (all p ≤ 0.021), peaking at Post-24 h (p = 0.021), but without difference across conditions (p = 0.135). Repeated intense decelerations during a multi-set repeated-sprint protocol exacerbated relative rectus femoris stiffness, accompanied by an increase in relative creatine kinase concentration immediately after sets, both remaining above Baseline at Post-72 h. Deceleration intensity should be considered to adequately prepare the musculotendinous system.